What should one do whose prayer is frequently assailed by doubts, such as whether he pronounced the opening Takbir, or recited a surah after Al-Fatiha, which compels him to interrupt and repeat his prayer, and sometimes to repeat his ablution to dispel the doubt?

The fundamental principle is that whoever doubts whether he has performed the Takbīrat al-Iḥrām (opening Allahu Akbar) or a pillar of the prayer while he is performing it, his prayer is not valid, and he must restart it. However, doubting the performance of a Sunnah, such as reciting a chapter after Al-Fātiḥah, does not necessitate interrupting the prayer.

Whoever doubts his wuḍūʾ (ablution) should act upon what he is certain of. If he is certain of purity and doubts the occurrence of an impurity, the default is that he is in a state of wuḍūʾ. If he is certain of impurity and doubts purity, the default is that he is in a state of impurity.

If these doubts become frequent and reach the point of obsessive whispering (waswasah), then it is obligatory to disregard them and not pay them any attention. Doubt after completing an act of worship has no effect.